荒漠绿洲湿地土壤水热盐动态过程及其影响机制

以甘肃临泽荒漠绿洲湿地为研究对象，通过对土壤温度、含水量、电导率及蒸散量的野外观测，在植物生长期和冻融期分别深入分析水热盐耦合运移过程及其影响因素，探讨水热梯度对盐分运移及其分布格局的控制作用。结果表明：土壤温度整体呈现出春夏季逐渐升高、秋冬季降低趋势。在冻结期，土壤表现为脱盐状态，表层电导率由2.8 mS·cm^-1降到1.2 mS·cm^-1；而在消融期为积盐状态，表层电导率由1.2 mS·cm^-1升到3.7 mS·cm^-1。在生长期，土壤含水量和电导率波动较为剧烈，表层含水量27%~43%，表层电导率3~5.5 mS·cm^-1，土壤脱盐、积盐反复出现。全年蒸散量总体呈单峰变化趋势，年蒸散量507 mm；土壤电导率与蒸散量呈正比关系，与地下水位呈负相关关系；蒸散发作用是土壤表层积盐的主要驱动力，而地下水波动影响着湿地脱盐、洗盐过程。因此，荒漠绿洲湿地土壤盐分累积过程是水分运移和热量传输过程发生变化的结果。

Dynamic Process of Water-Heat-Salt in Soil and the Mechanism in the Desert Oasis Wetland

The study was carried out at the desert oasis wetland in the middle reaches of China's Heihe River, where soil temperature, water content, electrical conductivity and evapotranspiration were measured to analyze the coupled transport of water-heat-salt and its influencing factors during the growing period and the freezing and thawing period, respectively, to discuss the controlling effects of the water-heat gradient on the migration process and the distribution pattern of salt. The results showed that soil temperature increased in spring and summer and decreased in autumn and winter. In the freezing period, soil desalinization was occurred. The surface electrical conductivity was reduced from 2.8 mS·cm^-1 to 1.2 mS·cm^-1. However, in the thawing period, soil salt accumulation was occurred. The surface electrical conductivity was increased from 1.2 mS·cm^-1 to 3.7 mS·cm^-1. During the growth period, the fluctuation of soil water content and electrical conductivity was significant, and showed the alternate appearance of desalination and salt accumulation. The surface water content ranged 27% to 43%, and the surface electrical conductivity ranged 3 mS·cm^-1 to 5.5 mS·cm^-1. The mean annual evapotranspiration totaled 507mm. And evapotranspiration showed a single peak trend. The relationship of the soil electrical conductivity and evapotranspiration was positively correlated. But the relationship of the surface electrical conductivity and groundwater depth was negatively correlated. Therefore, evapotranspiration was the main driving force of soil salt accumulation in soil surface, while the groundwater fluctuations affected the wetland desalination and the salt leaching process. Therefore, the accumulation of soil salinity in the desert oasis wetland was the result of the change of the water transport and the heat transfer.